Art of concentration of ores by flotation.



' flotation methods,

ART OF CONCENTRATION OF GEES BY FLOTATION.

menace.

No Drawing.

To all whom it may concern. Be it known that I, GEoRen D. VAN Ans- DALE, a citizen of the United States,

and State of New York, have invented certain new and useful Improvements in Art of Concentration of Ores by Flotation, of which the following is a specification.

My present invention is an improvement in the art of concentration of ores by flotation and relates particularly to the preparation of the ores to insure their proper concentration by flotation. t

It has been known that oxidized compounds of metals,.for .example, copper, are not readily concentrated by the ordinary but that such oxidized copper compounds may be converted into sulfids in various ways, and thereby rendered capable of being concentrated by flotation. One method of converting such oxidized compounds into sulfids is by introducing hydrogen sulfid into a pulp containing the ore to be concentrated in a finely divided or less complete conversion of the 'oxids into state. The result of this treatment is a more sulfids, theextent of this conversion being in some cases merely a film, and in others a more complete conversion, depending on the fineness of the mineral, the amount of hydrogen sulfid present, and other factors. For practical purposes a complete conversion is more desirable than a film, for the reason that for the flotation of'many ores it has been found necessary to add the oils during the milling operation. It is obvious that a film of sulfid even of quite an appreciablev thickness, will not be resistant to milling but will be abraded from. the core of oxid, the practical result being an incomplete extraction. In order to obviate this, it is necessary to add an excess of hydrogen sulfid, but it has been found that it is very difiicult to add just the exact amount required for the conversion of the copper, and that an excess of free hydrogen sulfid above such an amount is very detrimental to flotation.

It is necessary therefore to provide means for rendering such excess harmless in practical work, and such a means is described in these specifications and constitutes an improvement in the art.

I have heretofore spoken of copper ores,

and will describe this improvement as applied to such ores, but it can be readily understood that the same methods will apply 7 Specification of Letters Patent.

Application filed. February 7, 1916. Serial No. 76,757.

residing at New York, in the county of New York,

bearing materials,

' cally this excess cannot be Patented Aug, Ml, Mitt.

to ore other than copper, and Ido'not wish to confine the scope of this improvement therefore to copper ores only.

In experimenting with certain copper for example, slime tailings, in which a considerable part of the copper is in the oxidized condition, I have found that the amount of hydrogen sulfid necessary for complete conversion of such "oxids into sulfids, is not excessive, for example, in one class of material the amount needed is from 120% to 140% of the theoretical amount calculated from the amount of oxid copper present. I have also found that there is a more or less preferential action of such added hydrogen sulfid on the copper minerals present. That is to say, the oxidized copper compounds are first converted into sulfid, While there are still left remaining other constituents of the pulp capable of combining with free hydrogen I have foundtherefore that in order to convert all of the copper present into-sulfid compounds it is necessary to add at least the excess determined by assay on the material being treated to be necessary. Since practicontrolled exactly but can be controlled within certain limits, I have found that the amount of hydrogen sulfid added must be kept within the amount that can be absorbed by the other constituents of the pulp capable of reacting with hydrogen sulfid, and that when kept below this limit the excess will be readily neutralized and rendered harmless.

I have also found that, the element of time enters into the operation, that is to say, it is necessary to allow suflicient time first for the conversion of the oxids, and second to allow sufficient time for the absorption and neutralization of the excess hydrogen sulfid by the other constituents of the ore being treated.

This invention therefore consists in the discovery that a practical method of concentration as above outlined depends on the addition to the pulp of an amount of hydrogen sulfid sufiicient to convert all of the oxidcopper present to sulfid, together with an additional amount of the reagent not in mental hitherto may be rendered harmless,

first by controlling the amount as above, and

secondly by allowing a certain amount of time for its absorption and neutrahzatlon to take place.

With a pulp treated as outlmed above ii; is possible to et good concentration results by flotation ut without this method or other methods of rendering the excess hydrogen sulfid harmless, good results are not ob- In carrylng out this invention, the following apparatus and procedure may be used and followed, although of course modifications of both may be made.

The necessary steps of the operation are as follows, after suitable preliminary grinding, etc., of the material to be treated.

1. Generation of hydrogen sulfid. 2. Absorption of hydrogen sulfid by the 111 v p 3. Time of standing.

4. Flotation.

Practically the hydrogen sulfidmay be generated in any suitable way dependent on local conditions. One suitable method will be by the action of acid on low-grade copper iron matte, carrying say about 10% of copper. The undissolved residue from the action of the acid on such matte will contain all of the copper, gold and silver present,

and may accordingly be recovered and treated by smelting, thusreducing the cost of the necessary hydro en sulfid.

The hydrogen sul d may be brought into contact with the pulp in a closed vessel provided with means of agitating the pulp and with means for continuous supply and discharge of the pulp, and of continuous sup.- ply of the gas, which may preferably be under slight pressure. By suitably adjusting the supply and discharge of pulp and of gas to this vessel the amount of hydrogen sulfid needed may be kept within proper limits as described above, and as determined by assay in each individual case.

After treatment in this apparatus, the pulp may be conducted to another apparatus to allow time for the complete absorption of the excess of gas. This apparatus may be simply a closed tank, provided with means for agitation. Ordinarily from two to four hours time will be found sufiicient to absorb and neutralize all excess hydrogen sulfid..

After this step the pulp may be treated exactly as in ordinary flotation, that is to say, by addition of oil or other necessary reagent, and the operation of flotation carried out in any of the ordinary apparatus for the purpose.

In addition to the treatment of ores in which a part or all-of the minerals present are as oxids, the process will be found apglicable to other ores whose minerals have a lm of oxid only covering them. Ordinarily such ores are treated either by sufficient attrition to mechanically remove such films 4 of the mineral and the gangue constituents of an ore which consists in supplying hydrogen sulfid to the ore bearing. pulp to an amount in excess of the amount required for combination with the non-sulfid mineral present, in letting the pulp so treated stand until the excess hydrogen sulfidhas been absorbed, and in then separating the mineral and the gangue byflotation.

2. The process of separation by flotation of the mineral andthe gangue constituents of an ore which consists in adding hydrogen sulfid to the ore bearing pulp in suchquantity that it may all be utilized in combining with the mineral and other ingredients of the pulp, the quantity being in excess of the quantity for the mineral present, and in then separating the mineral and the gangue by flotation.

3. The process of separation by flotation of the mineral and the gangue constituents of an ore which consists in bringing hydrogen sulfid into contact with the pulp while the latter is agitated, in then permitting the pulp to stand, the quantity of hydrogen sulfid employed being in excess of the amount required for the proportion 'of mineral in the pulp, and in then separating the mineral and the gangue by flotation.

4. The process of separation by flotation of the'mineral and the gangue constituents of an ore which consists in supplying hydrogen sulfid to the ore bearing pulp, in letting the ore so treated stand until all free hydrogen sulfid has been absorbed, and in then separating the mineral and the gangue by flotation.

In testimony whereof I atfix my signature.

GEORGE nvn ARSDALE. [1,. 8-] 

